diff --git a/pkg/agentic/plan.go b/pkg/agentic/plan.go
index 93ab5e7..1455102 100644
--- a/pkg/agentic/plan.go
+++ b/pkg/agentic/plan.go
@@ -438,26 +438,11 @@ func (s *PrepSubsystem) planUpdate(_ context.Context, _ *mcp.CallToolRequest, in
 }
 
 func (s *PrepSubsystem) planDelete(_ context.Context, _ *mcp.CallToolRequest, input PlanDeleteInput) (*mcp.CallToolResult, PlanDeleteOutput, error) {
-	ref := planReference(input.ID, input.Slug)
-	if ref == "" {
-		return nil, PlanDeleteOutput{}, core.E("planDelete", "id is required", nil)
-	}
-
-	plan, err := readPlan(PlansRoot(), ref)
+	plan, err := archivePlanResult(input, "id is required", "planDelete")
 	if err != nil {
 		return nil, PlanDeleteOutput{}, err
 	}
 
-	path := planPath(PlansRoot(), plan.ID)
-	if !fs.Exists(path) {
-		return nil, PlanDeleteOutput{}, core.E("planDelete", core.Concat("plan not found: ", ref), nil)
-	}
-
-	if r := fs.Delete(path); !r.OK {
-		err, _ := r.Value.(error)
-		return nil, PlanDeleteOutput{}, core.E("planDelete", "failed to delete plan", err)
-	}
-
 	return nil, PlanDeleteOutput{
 		Success: true,
 		Deleted: plan.ID,
diff --git a/pkg/agentic/plan_compat.go b/pkg/agentic/plan_compat.go
index 0886ff3..36d9fe5 100644
--- a/pkg/agentic/plan_compat.go
+++ b/pkg/agentic/plan_compat.go
@@ -176,31 +176,11 @@ func (s *PrepSubsystem) planUpdateStatusCompat(ctx context.Context, _ *mcp.CallT
 }
 
 func (s *PrepSubsystem) planArchiveCompat(ctx context.Context, _ *mcp.CallToolRequest, input PlanDeleteInput) (*mcp.CallToolResult, PlanArchiveOutput, error) {
-	ref := planReference(input.ID, input.Slug)
-	if ref == "" {
-		return nil, PlanArchiveOutput{}, core.E("planArchiveCompat", "slug is required", nil)
-	}
-
-	plan, err := readPlan(PlansRoot(), ref)
+	plan, err := archivePlanResult(input, "slug is required", "planArchiveCompat")
 	if err != nil {
 		return nil, PlanArchiveOutput{}, err
 	}
 
-	now := time.Now()
-	plan.Status = "archived"
-	plan.ArchivedAt = now
-	plan.UpdatedAt = now
-	if notes := archiveReasonValue(input.Reason); notes != "" {
-		plan.Notes = appendPlanNote(plan.Notes, notes)
-	}
-	if result := writePlanResult(PlansRoot(), plan); !result.OK {
-		err, _ := result.Value.(error)
-		if err == nil {
-			err = core.E("planArchiveCompat", "failed to write plan", nil)
-		}
-		return nil, PlanArchiveOutput{}, err
-	}
-
 	return nil, PlanArchiveOutput{
 		Success:  true,
 		Archived: plan.Slug,
@@ -312,3 +292,32 @@ func planCompatibilityOutputStatus(status string) string {
 		return status
 	}
 }
+
+func archivePlanResult(input PlanDeleteInput, missingMessage, op string) (*Plan, error) {
+	ref := planReference(input.ID, input.Slug)
+	if ref == "" {
+		return nil, core.E(op, missingMessage, nil)
+	}
+
+	plan, err := readPlan(PlansRoot(), ref)
+	if err != nil {
+		return nil, err
+	}
+
+	now := time.Now()
+	plan.Status = "archived"
+	plan.ArchivedAt = now
+	plan.UpdatedAt = now
+	if notes := archiveReasonValue(input.Reason); notes != "" {
+		plan.Notes = appendPlanNote(plan.Notes, notes)
+	}
+	if result := writePlanResult(PlansRoot(), plan); !result.OK {
+		err, _ := result.Value.(error)
+		if err == nil {
+			err = core.E(op, "failed to write plan", nil)
+		}
+		return nil, err
+	}
+
+	return plan, nil
+}
diff --git a/pkg/agentic/plan_crud_test.go b/pkg/agentic/plan_crud_test.go
index ce02a61..695aaef 100644
--- a/pkg/agentic/plan_crud_test.go
+++ b/pkg/agentic/plan_crud_test.go
@@ -268,7 +268,12 @@ func TestPlan_PlanDelete_Good(t *testing.T) {
 	assert.True(t, delOut.Success)
 	assert.Equal(t, createOut.ID, delOut.Deleted)
 
-	assert.False(t, fs.Exists(createOut.Path))
+	assert.True(t, fs.Exists(createOut.Path))
+
+	plan, readErr := readPlan(PlansRoot(), createOut.ID)
+	require.NoError(t, readErr)
+	assert.Equal(t, "archived", plan.Status)
+	assert.False(t, plan.ArchivedAt.IsZero())
 }
 
 func TestPlan_PlanDelete_Bad_MissingID(t *testing.T) {
diff --git a/pkg/agentic/prep.go b/pkg/agentic/prep.go
index 660c733..1cd2073 100644
--- a/pkg/agentic/prep.go
+++ b/pkg/agentic/prep.go
@@ -185,7 +185,7 @@ func (s *PrepSubsystem) OnStartup(ctx context.Context) core.Result {
 	c.Action("plan.update", s.handlePlanUpdate).Description = "Update plan status, phases, notes, or agent assignment"
 	c.Action("plan.update_status", s.handlePlanUpdateStatus).Description = "Update an implementation plan lifecycle status by slug"
 	c.Action("plan.archive", s.handlePlanArchive).Description = "Archive an implementation plan by slug"
-	c.Action("plan.delete", s.handlePlanDelete).Description = "Delete an implementation plan by ID"
+	c.Action("plan.delete", s.handlePlanDelete).Description = "Archive an implementation plan by ID"
 	c.Action("plan.list", s.handlePlanList).Description = "List implementation plans with optional filters"
 	c.Action("phase.get", s.handlePhaseGet).Description = "Read a plan phase by slug and order"
 	c.Action("phase.update_status", s.handlePhaseUpdateStatus).Description = "Update plan phase status by slug and order"